1900-05, Americanism; compared with GermanFink literally, finch, colloquial epithet for an undesirable person, especially an untidy or loose-living one (often in compounds, as Duckfink sycophant, Schmierfink untidy writer); but the transmission of this word to English and the range of meanings of the English word have not been clarified fully

1902, of uncertain origin, possibly from German Fink "a frivolous or dissolute person," originally "finch;" the German word also had a sense of "informer" (cf. stool pigeon). The other theory traces it to Pinks, short for Pinkerton agents, the private police force hired to break up the 1892 Homestead strike. As a verb, 1925 in American English slang. Related: Finked; finking.